After brain trauma from an accident, brain cells die from lack of oxygen. It is thought that many of these cells can be revived through hyperbaric oxygen therapy. A 1975 clinical trial of 99 patients with brain trauma in the mid-brain found that HBO therapy decreased mortality by 40%. A 1990 Study by Richard Neubauer, M.D., found that neurons can be reactivated up to 14 years after a traumatic injury. Specialized brain imaging found increased metabolic activity after even just one session of HBO.